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Siberian snakes that consist of four helical dipole magnets will be installed in the Relativistic Heavy Ion Collider (RHIC) to preserve the polarization of the proton beam. To promote this project we are collaborating with Brookhaven National Laboratory (BNL) in studying helical magnet designs. At present, two types of helical magnets are being developed. One is being designed by the BNL magnet group, and the other by Advanced Magnet Technology (AML), Inc. These magnets use the same superconducting cable but have different shapes especially in the end regions. We are evaluating the performance of both magnet designs using the three dimensional (3D) magnetic field analysis code TOSCA. In particular, saturation effect, field strength, multipole component and magnet quenching features will be discussed.

An "RI beam factory" has started to be contracted as the next project of the RIKEN Accelerator Research Facility (RARF). The "RI beam factory" aims at production and acceleration of radioactive isotope beams covering the whole mass region. It requires the energy of ion beam to be higher than 100 MeV/nucleon. To accomplish this requirement, the following two ring cyclotrons have been adopted as post-accelerators of the existing RIKEN ring cyclotron (RRC): a 4-sector ring cyclotron for the first stage (IRC) and a 6-sector superconducting ring cyclotron for the second stage (SRC). The sector magnet of the SRC has to be flexible enough to generate isochronous fields in a wide range of energies and for various q/A values. In this report we describe the isochronous field generation and orbit analysis of the SRC.

A 6 T superconducting solenoid has been constructed to focus heavy ion beams on the production target of radio isotope beams. The design field on axis is 6.2 T with an average current density of 9,600 A/cm/sup 2/. The overall coil length is 1.1 meter, and the coil is divided into three equal-length sections to ease winding and to reduce IR drop through diode connection. A main feature of the system is that the solenoid is conductively cooled by a cryocooler directly attached onto the center coil without liquid helium involved. The solenoid was successfully trained to 6.2 T, and its optical properties were tested in the beamline at RIKEN. The design features and the test results are presented.